Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1887-08-24
rbcartesiou.weI,s Problem.
R1cuno.p.VA.. August %, 1887.

JhcArtesiap-weIis Problem.
RIcuMoHD, VA, August Y, 1887.
TO me Edifor of the Dispatch:
1 have been much gratifed at the in
terest manifested in the problem OF the
Artesian wells, by yourself edtorially,
by several correspondents, and, may
add. by a number of friends who have
spoken to me personally on the sub
icct. Nor can / be insensible to the
very kind terms in which, led by your
self, these correspondents and friends
have referred TO myself in this connec-
ton.
Especially should thank your cor
respondent, &C." who originally pro-
pounded the problem, both for his for
bearance under my hard cross-question-
ings, and for the satisfactory answer
which he has given to some. at least, OF
the questions asked.
1t seems TO me that with the light
thrown upon the problem by "P. II.
e." who very pcrtipently sdduces the
views of Charles Darwin on similar
case, and by an anonymous cold
Pupil OF mine who gives substantially
remembered explanation OF CORE
spending phenomena observed in the
Charleston IS. c. well, the solution is
not difficult.
TO clear the way / may say word
as TO Artesian wells generally. What
is an Artesian well? / would answer.
with 10 attempt at precision, deep
well generally very deep, and usually
bored and Of small diameter), in which
the water rises, OF its own accord, up
10 or above the surface. What are the
conditions necessary for such a well?
As usually given they are these There
must lie under the point where the well
is to lie bored three strata, parallel to
each other. and having the following
| characteristics
!. They must all be concave or bowl
shaped; and the point for the we'll
must be somewhere in the hollow of
the bowl, but at much lower eleva-
ton than the upper edges OF the
bowl.
9. TIE upper stratum, which we will
call No. ], and the lowest, which we
will call No. 3, must both be impervious,
or able to hold water.
Between these two imporyiOus strata
| must be one Of sand or gravel, OF Il
loose-textured rock into ana through
which water can somewhat freely pass.
Cal tlls No. >. These strata may be
few miles or hundreds of miles in
extent, and may be few feet or thou
sands Of feet in thickness, and may
have much irregllarity OF thickness,
form, end structure, &c, hut must be
substantially as l have stated. Nor
must it be thought that such special
arrangement Of strata must necessarily
he rare for We have here in Richmond
many alternate pervious and imper-
yious strata, and TO this alienation all
our springs are due.
Now as the rain falls on the exposed
edge or Outcrop OF No. 2 (which edge
all around may be hundreds of square
miles in cxtent), it settles down be-
| tween No ! and No. 3 neither of which
will permit it to pass, and fills up and
saturates completely the porous No. 2,
with veins and channels here and there
perhaps. Suppose, now, some one
living in the hollow of this double
bottomed bowl bores down till he gets
through the hard No. and strikes the
porous No. 2 it is clear that the pressure
Of the water, which fills mp the bowl to
itsedees, will force upG stream through
the boring Us high Theoretically as
those edges themselves are just rs the
fountain on the Square might he ex
pocted 10 rise az high as the level Of
the Reservoir. Permit me t. give ~
illustration that l have often u,cd
Take basin or deep plate-tb's Is 80
3 I'll even full with sand-th- Is 70
.; press far down into the san / a drci
saucer Of earth-this is No. l. Poul
water on The exposed edges Of shc sane
iii it is saturated. Vow imagine hol,
bored through the earth IL the saucer
Int not through the saucer; that wOuIC
be an ordinary well But lot The hol'
90 down through the saucer, and tia
would be an AItesian wei, and il pireC
the water should rise in 1t ncafly ~ t,
the height Of the sand.
But TO our problem, "Nliy do tn
West Point wells ebb and flow with tn
tide?" / suppose these wells an
Others on the Atlantic coast are bored
not on three bowl shaped strata, but OF
strata that simply incline towards tn
ocean, and that the ocean itself form
the western side of the bowl. On
Richmond granite may be the No. , t
hold the water for the West Point wells
and the rain falling on this flows slowl,
down it into the ocean under some No
u, discharging itself. perhaps at grea
depth, and flowing only by the dWer
cncc Of ievct between its starting poin
at the upper edge of the stratum an
, the level Of the ocean.
We must have the idea, then, of th
, water bearing stratum, No. 2, abuttin
deep down against the ocean, int
| which it slowly pOurs its waters, Will
| more water comes in steadily from tn
9 higher part of the slope on the east
; and that at West Point there is an W
t ward pressure on the everything No.
| due 10 the combined effect of the heigl
D of the water in No. on the east an
: the level of the ocean on the ives
This pressure causes the water to ris
Q in the West Point wells.
g Now let the ocean level rise-say fou
5 feet with the tide the upward pressur
( al West Point and elsewhere rises also
and more water flows from the we'll
and gicc Ccrsd as the tide recedes. i
illustrate further, take Ushaped tul
and let one leg-say the right, be fex
:. lie. Fore a hole i'll the hollow of til
4 L and insert fine glass tube as
r gauge. Let water run in the right sid
T 10 keep it full while it runs out {
It the right flexible side. Now raise an
lower this flexible side (or better, let Il
1 flexible tube dip into q cup of waite
s and then raise and lower this cup, an
the water will rise and fall in the gaue
z tube accordingly.
d The application is easy The left i
o is the sloping No. 2 entubed betwee
d and 8. The small gauge tube is ii
" Wei and the right flexible leg (or IL
j. cup OF water the ocean. The raisir
= ard lowering Of this leg Tor the GU
It answer to the tides, and the rising al
falling of the level in the gauge is Il
d ebbiDg and flowing Of The wells, whit
= respond TO them.
& am aware, Mr.. Editor, of many il